Electronic digital displays

ABSTRACT

A digital display device for displaying a plurality of alphanumeric characters from a single electronic display unit in which the single unit is reciprocated at a predetermined frequency through a given distance and the unit is energized to emit an alphanumeric character display at synchronized positions during its swing between extreme positions so that the complete display of alphanumeric characters appears without the eye being able to detect the motion of the single display unit.

0 United States Patent 1 n] 3,846,784 Sinclair Nov. 5, 1974 ELECTRONICDIGITAL DISPLAYS Rl8,76l 3/1933 Centeno l78/7.6

[76] Inventor: Clive Marles Sinclair, 18 Newton P E J h W C M H Rd., C bd E 1 d rlmary xammero n a we am n ge ng an Assistant Examiner-MarshallM. Curtis Flledi y 7, 1973 Attorney, Agent, or FirmYoung & Thompson 21Appl. No.: 357,719

ABSTRACT [30] Foreign Application Priority Data A digital display devicefor displaying a plurality of al- May 22, 1972 Great Britain 23893/72PhamumeriC Characters from a Single electronic p y unit in which thesingle unit is reciprocated at a prede- 52 us. c1 340/336, 340/324 R,340/373 termined frequency through a given distance and the 511 Int. Cl.G09f 9/32 unit is energized to emit an alphanumeric Character [58 Fieldof Search 340/24, 49, 324 R, 378 R, p y at Synchronized Positions duringits swing 340/373, 336; l78/7 6 tween extreme positions so that thecomplete display of alphanumeric characters appears without the eye [5 Rf n Cited being able to detect the motion of the single display UNITEDSTATES PATENTS 3,555,505 1/1971 Srogi 340/24 11 Claims, 5 DrawingFigures PATENTEU 5 I974 sum 1 or 4 3 a. a u a PATENTEDNBV 5 1974 3846784SHEET 2 OF 4 1 ELECTRONIC DIGITAL DISPLAYS The present invention relatesto electronic digital displays.

Equipment which displays information electronically is widely known andused, and there is a demand for electronic components which acceptelectrical signals and display either letters or numbers; An electroniccalculator of known type contains eight such components each capable ofdisplaying any of the digits from O to 9. Each display unit consists ofa seven bar arrangement, the seven individual bars being separatelyilluminated and arranged in the shape of a square eight. With thisarrangement the calculator is able to display any eight figure number.In addition, this type of display unit can be easily adapted to displayletters as well as numbers.

However, the above described alphanumeric or numeric display devices arerelatively expensive especially when one needs six or more in order toachieve the desired digital display.

It is therefore an object of the present invention to reduce thisexpense by utilizing only a single display device in order to obtain adisplay of a plurality of digits.

According to the present invention there is provided a digital displaydevice capable of displaying a plurality of numbers and/or lettersincluding a single electronic digital display unit. means forreciprocating said unit at a predetermined frequency through a givendistance and means for causing a plurality of discrete electronicdisplays to be emitted from said display unit at precise positions inthe swing of the unit from one extreme position to the other.

Preferably in one form the means for reciprocating said display unitincludes a U-shaped piece of springy material to one extremity of whichis attached an arm on the end of which the display device is mounted,and to the other extremity of which is attached adjustable counterweight means. Said counter weight means may comprise a threaded rod uponwhich a nut is threadably engaged such that it may be screwed in eitherdirection along the threaded rod. Means may be provided for theaforesaid assembly to be lightly gripped in resilient pads at the baseof the U and excited into oscillation in the manner of a tuning fork bythe interaction of the field of an electro-magnet with a pole pieceattached to one arm of the U.

Preferably in another form the means for reciprocating said display unitincludes two lever arms pivotally attached one to the other at abouttheir centres in the manner of a pair of scissors. the pivot point beingfixedly attached to the casing of the display. The digital displaydevice and the counterweight may be mounted on respective ends of thetwo lever arms. Between the other ends of the lever arms and the pivotpoint there may be mounted firstly a spring fixed at its outer ends tothe two lever arms and at its centre to the instrument case and actingso as to maintain the adjacent lever arms at an appropriate angle one toanother and secondly a solenoid associated with two pole pieces eachbeing attached to one of the lever arms such that when the adjacentlever arms move closer to one another the pole pieces move furtherintothe solenoid.

Preferably the means for causing a plurality of discrete electronicdisplays to be emitted from said display unit at precise positions inthe swing of the unit comprises a synchronizing circuit driven from adisplay oscillator and controlling the phase and frequency of the clockoscillator driving the calculator logic.

Preferably means are provided to speed up and slow down the clockoscillator by detection of the display digit position, this controlensuring even spacing of the displayed digits in spite of the sinusoidalvariation of the digit velocity.

The present invention will now be described in greater detail by way ofexample with reference to the accompanying drawings, wherein:

FIG. 1 shows a front elevation of one preferred form of the mechanicalarrangement of the display according to the present invention;.

FIG. 2 is a section along the line II of FIG. 1;

FIG. 3 shows a front elevation of the mechanical arrangement of a secondpreferred form of the display according to the present invention;

FIG. 4 shows in functional block diagrammatic form the driving circuitryfor the displays of FIGS. 1 to 3;

' and FIG. 5 shows some of the waveforms relating to FIG. 4.

Referring to FIG. 1 the mechanical arrangement of a first form of thedisplay according to the present invention comprises a one digitelectronic display 21 mounted on the end of an arm 23, the arm 23 beingI which in turn is fixed to the instrument casing (not shown). Themounting of the U-shaped component 24 is such as to retain it inposition whilst permitting sufficient movement at the mounting point toenable a torque to be transmitted from one side of the mounting to theother thus enabling the assembly of the U component 24 in conjunctionwith the rod 25 carrying the nut 26 and the arm 23 carrying the digitdisplay 21 to behave as a tuning fork.

The arm of the U-shaped component 24 which carries the arm 23 and thedigit electronic display 21, has a pole piece 27 secured thereto nearthe extremity of said arm of the U-shaped component 24. A solenoid 29 ismounted on a block 30 which in turn is mounted on the instrument case(not shown). Associated with the solenoid 29 is a feedback coil 28 whichis wound on the same former as the solenoid winding. The purpose of thisfeedback coil 28 will be explained in greater dethe digit display 21 areattached to the arm 23 and are connected to the driving circuits viaconnection points (not shown) on the mounting block 35. Furtherconnections are made to the driving solenoid 29 and the feedback coil28. Adjustment of the nut 26 on the threaded rod 25 enables the two armsof the tuning fork" to be balanced, ie the moment about the mountingpoint due to movement of the short heavy arm 25 is matched by the momentapplied by the long fine arm 23 and display digit 21.

The sectional view of the assembly of FIG. 1 shown in FIG. 2 makes clearthe arrangement whereby the U component 24 made of a flat strip of aspringy metal is held by the resilient pads 33 and 34 which are clampedbetween the blocks 31 and 32.

The mechanical arrangement of a second preferred form of the displayaccording to the present invention is shown in FIG. 3 wherein a resonantmechanical system is comprised by arms 41 and 44 in conjunction with aspring 45.

The arms 41 and 44 are coaxially pivoted on a pivot 42 which pivot isattached to the instrument casing (not shown). At one end of the arm 41is mounted a display digit 40, the adjacent end of arm 44 bearing acounter weight 43. The arms 41 and 44 are held at a suitable mean angleone to the other by the spring 45 the centre of the spring 45 beinglocated with respect to the instrument casing by a resilient peg 46.

The resonant assembly is excited into motion by a solenoid 48 attractinginto it pole pieces 47 and 49 which are attached to the arms 41 and 44respectively. The

' solenoid 48 has wound coaxially with it a position feedback coil 51and is mounted on the instrument case by means of a mounting block 50.Fine gauge wires feed the required signals to the digit display 40 andare led along the arm 41 towards the pivot point 42 in the region ofwhich they are terminated at suitable connection pins (now shown).

The operation of the display will now be explained with reference to theremaining figures of the accompanying drawings whereof FIG. 4 is afunctional block diagram and'FIG. 5 shows some of the waveformsappertaining to the blocks of FIG. 4.

In the following description the following components in the twoembodiments of mechanical systems described above have the followinggeneral designation for the sake of simplicity.

The one digit displays 21 and 40 are designated 1.

The seven individual segments of the display 1 are designated 2.

The arms 23 and 41 are designated 3.

The pole pieces 27 and 47/49 are designated 4.

The position feedback coils 28 and 51 are designated 6. The solenoids 29and 46 are designated 7.

The digit display 1 is mounted at the end of the arm 3 and comprisesseven segments 2 arranged in the form ofa square eight, these segmentsbeing individually illuminated according to the output from theelectronic circuit.

The display driving system of FIG. 4 comprises a display driveoscillator 85 a calculator oscillator 9; a synchronizing circuit 10; aflyback blanking circuit 11; a gate circuit 12; a monostable drivercircuit 13; a calculator integrated circuit 14, hereinafter referred toas the calculator chip; a segment driver circuit 15 and asynchronization gate 16. Timing of circuit operations is controlled fromthe free running oscillator 8 which drives the solenoid 7 at theresonant frequency of the mechanical system of which the arm 3 is apart. setting the display digit 1 into oscillatory motion. The segmentsof the display digit 1 are driven according to the number to bedisplayed from the segment outputs of the calculator chip 14 via thesegment driver 15. Whilst which segments are to be displayed isdetermined by the calculator output, illumination of the display iscontrolled by the state of the monostable driver 13 which switches thedisplay on at appropriate instants.

The calculator clock oscillator 9 is synchronized in accordance withdigit position by means of the synchronizer 10 which is fed the outputsignal of the driving oscillator 8 as well as a signal corresponding tooutput of the first display digit. The function of the synchronizer 10is to compare the two aforesaid input signals and produce an outputsignal capable of controlling the oscillator 9 to synchronize the outputof the first display digit from the calculator chip 14 with one endposition of the display digit 1. A further control of the calculatorclock oscillator 9 is provided by the digit position feedback winding 6adjacent to the driving solenoid 7. The correction applied to the clockoscillator 9 by the output of the winding 6 serves to speed up and slowdown the clock oscillator 9 to produce an even spacing of the displayeddigits in a manner analogous to the S-correction employed in televisionreceivers. When the display digit 1 is at the end of its swing it ismoving slowly relative to its speed of movement at the centre of itsswing and thus to produce an even spacing of the digits throughout thedisplay digits swing the S- type correction applied by the winding 6slows the clock oscillator 9 when the display digit approaches the endof its swing and speeds up the clock oscillator 9 when the display digitapproaches the centre of its swing.

In order to stop the motion of the display digit 1 when a number isilluminated, i.e., to make the displayed number appear stationary, thedisplay is lit for a short period only when a digit output from thecalculator indicates the selection of segments corresponding to a numberto be displayed has been made. The calculator digit outputs drive theshort period monostable 13 via the gate 12 which gate prevents themonostable 13 from driving the display digit 1 when the flyback blankingcircuit 11 driven by the oscillator 8 detects flyback of the displaydigit 1. Thus the display digit 1 displays on the appropriate segments 2the calculator output during one half of its cycle of oscillation. Thefunction of the gate 16 is to permit only the first displayed digitpulse to be fed to the synchronizer 10 so that it does not attempt tore-synchronize the clock oscillator 9 on receipt of each digit output.

The operation of the circuitry of FIG. 4 will now be further explainedby reference to FIG. 5 wherein waveform (a) shows the square wave outputof the flyback blanking circuit 11 of FIG. 4, the output level being-high during the forward displaying stroke of the display digit and low"during the return stroke of the display digit thus preventing thedisplay from lighting up during the return stroke of the display digit.During the forward stroke of the display digit, the digit outputs fromthe calculator chip 14 pass via the gate 12 (opened by the output of theflyback blanking circuit 11 as described above) to the monostable driver13 the output waveform of the gate 12 being illustrated in waveform (b)which shows the series of digit pulses. To provide the very shortduration pulses required to stop the motion of the display digit theleading edge of each digit pulse triggers the monostable driver 13 thismonostable having the required short pulse width and producing waveform(c).

The waveforms (a), (h) and (c) of FIG. 5 are drawn to a timescale twhich neglects the variation in clock oscillator speed effected byS-correction. Taking this effect into account the display drive pulsesare plotted against a real time axis T as shown in waveform (11). Thiswaveform clearly shows their increased frequency towards the centre ofthe display, at which point the digit is moving at its maximum rate.When the display is driven by the waveform (d) of H6. 5, the digitsappear evenly spaced out.

What I claim and desire to secure by Letters Patent l. A digital displayapparatus for displaying a plurality of alphanumeric charactersincluding: a single electronic display unit having a plurality ofindividual segments which can be separately illuminated; an arm carryingthe electronic display unit at one end thereof; means for mounting saidarm so that the end of the arm carrying the display unit can be made toreciprocate through a given are of a circle; means defining a pluralityof spaced positions along the arc of the circle at which the requiredsequence of alphanumeric characters can be displayed from the singledisplay unit; display unit reciprocating means energized at a givenfrequency to cause a given periodicity of reciprocation to the end ofthe arm carrying the display unit; means for energizing the appropriateindividual segments of the display unit at precise moments as the unitpasses each s of the spaced positions during each reciprocation, saiddisplay unit energizing means being synchronized with the reciprocationof the arm so that the positions of display are identical from onereciprocation to the next, whereby a series of alphanumeric charactersare continuously visible due to persistance of vision.

2. A digital display apparatus according to claim 1, wherein the meansfor reciprocating said display unit comprises: a U-shaped component madeof a springy material, to one extremity of which is attached the arm; anadjustable counterweight attached to the other end of the U-shapedcomponent; resilient pads for lightly gripping the U-shaped component ata point about the base of the U; a fixed electro-magnet; and acooperating pole piece attached to one arm of the U-shaped component forexciting the U-shaped component into oscillation in the manner of atuning fork by the interaction of the electro-magnet and its associatedpole piece. v

3. A digital display device according to claim 2, wherein the adjustablecounter weight means comprises a threaded rod and a nut, the nut beingthreadably engaged on the rod such that the nut may be screwed in eitherdirection along the rod.

4. A digital display apparatus according to claim 1, wherein said arm,carrying the display unit at one end, is formed integrally with a firstarm of a pair of lever arms, a pivot point located on the casing of thedisplay device and arranged substantially centrally of the pair of leverarms whereby the arms can individually pivot about said pivot point inthe manner of a pair of scissors, a counterweight being attached to anend of the other arm which does not carry the display unit.

5. A digital display device according to claim 4, including a solenoidfixed to the casing of the display; a spring attached at its outer endsto the two lever arms and at its centre to the casing of the display;and two pole pieces secured to the respective arms, the pole piecesbeing associated with the solenoid such that when the solenoid isenergized, the pole pieces are atthe display oscillator; means forgenerating electrical signals representing the required sequence ofalphanumeric characters to be displayed; means for switching on and offsaid generated signals in synchronism with the reciprocation of thedisplay unit whereby the required sequence of alphanumeric characters isdisplayed over a complete swing of the display unit from one extremeposition to the other. v

7. A digital display apparatus according to claim 6, additionallyincluding means for generating a feedback signal proportional to theposition of the display unit in order to firstly decrease the frequencyof the output signals to the display unit as the display unit approachesthe extreme positions of its swing, and secondly, to increase thefrequency of the output signals as the display unit approaches the meanposition of its swing, whereby a substantially equi-spaced alphanumericdisplay can be obtained.

8. A digital display apparatus according to claim 1, comprising: a firstoscillator; an electro-magnet energized by said oscillator; a pole piecelocated on said arm and electro-magnetically associated with saidelectro-magnet for driving said arm in synchronism with the frequency ofthe oscillator; a calculator inegrator circuit in which the alphanumericsequence to be displayed is calculated; a segment drive circuitcntrolled from the calculator integrator circuit to enable the correctsegments of the display unit to be energized according to eachalphanumeric character to be displayed; a second oscillator controllingthe calculator integrator circuit; and a synchronizing circuitcontrolled from the first oscillator for ensuring synchronous runningbetween the two oscillators.

9. A digital display apparatus according to claim 8, additionallyincluding: a fiyback blanking circuit controlled fromsaid firstoscillator; a gate circuit controlled from the fiyback blanking circuit,said gate circuit passing the output from the calculator integratorcircuit when unblocked; and a monostable driver circuit connectedbetween said gate circuit and the display unit, whereby the dispaly unitis not energized during the return movement of the reciprocating arm,due to the gate being blocked.

10. A digital display apparatus according to claim 8, additionallyincluding a synchronization gate located between a first output of thecalculator integrator circuit and the synchronizing circuit, wherebyonly the first displayed alphanumeric character controls thesynchronization of the calculator integrator through the secondoscillator with the first oscillator.

11. A digital display apparatus according to claim 8, wherein saidsecond oscillator is also controlled from the position of the displayunit through electromagnetic coupling means, whereby the frequency ofthe output signals to the display unit is decreased as the display unitapproaches the extreme positions of its swing and increased in the meanposition of its swing,

so as to produce a substantially equi-spaced alphanumeric display.

1. A digital display apparatus for displaying a plurality ofalphanumeric characters including: a single electronic display unithaving a plurality of individual segments which can be separatelyilluminated; an arm carrying the electronic display unit at one endthereof; means for mounting said arm so that the end of the arm carryingthe display unit can be made to reciprocate through a given arc of acircle; means defining a plurality of spaced positions along the arc ofthe circle at which the required sequence of alphanumeric characters canbe displayed from the single display unit; display unit reciprocatingmeans energized at a given frequency to cause a given periodicity ofreciprocation to the end of the arm carrying the display unit; means forenergizing the appropriate individual segments of the display unit atprecise moments as the unit passes each of the spaced positions duringeach reciprocation, said display unit energizing means beingsynchronized with the reciprocation of the arm so that the positions ofdisplay are identical from one reciprocation to the next, whereby aseries of alphanumeric characters are continuously visible due topersistance of vision.
 2. A digital display apparatus according to claim1, wherein the means for reciprocating said display unit comprises: aU-shaped component made of a springy material, to one extremity of whichis attached the arm; an adjustable counterweight attached to the otherend of the U-shaped component; resilient pads for lightly gripping theU-shaped component at a point about the base of the U; a fixedelectro-magnet; and a cooperating pole piece attached to one arm of theU-shaped component for exciting the U-shaped component into oscillationin the manner of a tuning fork by the interaction of the electro-magnetand its associated pole piece.
 3. A digital display device according toclaim 2, wherein the adjustable counter weight means comprises athreaded rod and a nut, the nut being threadably engaged on the rod suchthat the nut may be screwed in either direction along the rod.
 4. Adigital display apparatus according to claim 1, wherein said arm,carrying the display unit at one end, is formed integrally with a firstarm of a pair of lever arms, a pivot point located on the casing of thedisplay device and arranged substantially centrally of the pair of leverarms whereby the arms can individually pivot about said pivot point inthe manner of a pair of scissors, a counterweight being attached to anend of the other arm which does not carry the display unit.
 5. A digitaldisplay device according to claim 4, including a solenoid fixed to thecasing of the display; a spring attached at its outer ends to the twolever arms and at its centre to the casing of the display; and two polepieces secured to the respective arms, the pole pieces being associatedwith the solenoid such that when the solenoid is energized, the polepieces are attracted into opposite ends of the solenoid thus moving thearms closer together.
 6. A digital display apparatus according to claim1, wherein the means for causing a plurality of discrete alphanumericdisplays to be emitted from said display unit at precise positions alongthe arc over which the display unit reciprocates comprises: anoscillator providing a constant frequency to drive the display unitreciprocating means; a synchronizing circuit driven from the displayoscillator; means for generating electrical signals representing therequired sequence of alphanumeric characters to be displayed; means forswitching on and off said generated signals in synchronism with thereciprocation of the display unit whereby the required sequence ofalphanumeric characters is displayed over a complete swing of thedisplay unit from one extreme position to the other.
 7. A digitaldisplay apparatus according to claim 6, additionally including means forgenerating a feedback signal proportional to the position of the displayunit in order to firstly decrease the frequency of the output signals tothe display unit as the display unit approaches the extreme positions ofits swing, and secondly, to increase the frequency of the output signalsas the display unit approaches the mean position of its swing, whereby asubstantially equi-spaced alphanumeric display can be obtained.
 8. Adigital display apparatus according to claim 1, comprising: a firstoscillator; an electro-magnet energized by said oscillator; a pole piecelocated on said arm and electro-magnetically associated with saidelectro-magnet for driving said arm in synchronism with the frequency ofthe oscillator; a calculator inegrator circuit in which the alphanumericsequence to be displayed is calculated; a segment drive circuitcntrolled from the calculator integrator circuit to enable the correctsegments of the display unit to be energized according to eachalphanumeric character to be displayed; a second oscilLator controllingthe calculator integrator circuit; and a synchronizing circuitcontrolled from the first oscillator for ensuring synchronous runningbetween the two oscillators.
 9. A digital display apparatus according toclaim 8, additionally including: a flyback blanking circuit controlledfrom said first oscillator; a gate circuit controlled from the flybackblanking circuit, said gate circuit passing the output from thecalculator integrator circuit when unblocked; and a monostable drivercircuit connected between said gate circuit and the display unit,whereby the dispaly unit is not energized during the return movement ofthe reciprocating arm, due to the gate being blocked.
 10. A digitaldisplay apparatus according to claim 8, additionally including asynchronization gate located between a first output of the calculatorintegrator circuit and the synchronizing circuit, whereby only the firstdisplayed alphanumeric character controls the synchronization of thecalculator integrator through the second oscillator with the firstoscillator.
 11. A digital display apparatus according to claim 8,wherein said second oscillator is also controlled from the position ofthe display unit through electro-magnetic coupling means, whereby thefrequency of the output signals to the display unit is decreased as thedisplay unit approaches the extreme positions of its swing and increasedin the mean position of its swing, so as to produce a substantiallyequi-spaced alphanumeric display.